Internal structures and compositions of (giant) exoplanets Tristan - - PowerPoint PPT Presentation

Internal structures and compositions of (giant) exoplanets

Tristan Guillot (OCA, Nice)

Exoplanets in Lund Lund 6-8 May 2015

Linking interior & atmospheric composition

If c lo an 209458b

Interior Atmosphere

Linking interior & atmospheric composition

Moutou et al. (2013) Madhusudhan et al. (2014)

If c lo an 209458b

0.1 1.0 10.0 100.0 Mass / MJup 5 10 15 Radius / 10

• l

• c
• r

• c
• r

• c
• r

• r

Interior Atmosphere

Outline

• Jupiter & Saturn
• Theoretical considerations
• Giant exoplanets
• Perspectives

Jupiter & Saturn

Constraints on atmospheric composition

Interior compositions

Jupiter

Molecular H2 (Y~0.23) Metallic H

+

(Y~0.27)

Helium rain

165-170 K 1 bar 6300-6800 K 2 Mbar 15000-21000 K 40 Mbar

Saturn

Molecular H2 (Y~0.20?) Metallic H

+

(Y~ 0.30?)

Helium rain

135-145 K 1 bar 5850-6100 K 2 Mbar 8500-10000 K 10 Mbar Ices + Rocks core ?

Interior compositions

2 4 6 8 10 MZ/MEarth 5 10 15 20 25 30 Mcore/MEarth

a t m

• s

p h e r i c atm + 8xSolar(H2O) 8xSolar(Z elements)

1 Mbar 1 Mbar 2 Mbar 2 Mbar 3 Mbar 3 Mbar 4 Mbar 4 Mbar 1 Mbar 2 Mbar "Slow" "Slow" Forbidden region "Fast"

Interior compositions

2 4 6 8 10 MZ/MEarth 5 10 15 20 25 30 Mcore/MEarth

a t m

• s

p h e r i c atm + 8xSolar(H2O) 8xSolar(Z elements)

1 Mbar 1 Mbar 2 Mbar 2 Mbar 3 Mbar 3 Mbar 4 Mbar 4 Mbar 1 Mbar 2 Mbar "Slow" "Slow" Forbidden region "Fast"

Fortney & Nettlemann (2010) Helled & Guillot (2013)

Interior compositions

2 4 6 8 10 MZ/MEarth 5 10 15 20 25 30 Mcore/MEarth

a t m

• s

p h e r i c atm + 8xSolar(H2O) 8xSolar(Z elements)

1 Mbar 1 Mbar 2 Mbar 2 Mbar 3 Mbar 3 Mbar 4 Mbar 4 Mbar 1 Mbar 2 Mbar "Slow" "Slow" Forbidden region "Fast"

Interior compositions

2 4 6 8 10 MZ/MEarth 5 10 15 20 25 30 Mcore/MEarth

a t m

• s

p h e r i c atm + 8xSolar(H2O) 8xSolar(Z elements)

1 Mbar 1 Mbar 2 Mbar 2 Mbar 3 Mbar 3 Mbar 4 Mbar 4 Mbar 1 Mbar 2 Mbar "Slow" "Slow" Forbidden region "Fast"

Interior compositions

2 4 6 8 10 MZ/MEarth 5 10 15 20 25 30 Mcore/MEarth

a t m

• s

p h e r i c atm + 8xSolar(H2O) 8xSolar(Z elements)

1 Mbar 1 Mbar 2 Mbar 2 Mbar 3 Mbar 3 Mbar 4 Mbar 4 Mbar 1 Mbar 2 Mbar "Slow" "Slow" Forbidden region "Fast"

Interior compositions

2 4 6 8 10 MZ/MEarth 5 10 15 20 25 30 Mcore/MEarth

a t m

• s

p h e r i c atm + 8xSolar(H2O) 8xSolar(Z elements)

1 Mbar 1 Mbar 2 Mbar 2 Mbar 3 Mbar 3 Mbar 4 Mbar 4 Mbar 1 Mbar 2 Mbar "Slow" "Slow" Forbidden region "Fast"

Theoretical considerations

The low-Z content of accreted gas

Pollack et al. (1996)

The low-Z content of accreted gas

In standard core-accretion models, most of the heavy elements are accreted during the core growth

• phase. (A small fraction is accreted during the

envelope collapse phase, when the increased gravitational reach brings a fresh supply of planetesimals).

Pollack et al. (1996)

The low-Z content of accreted gas

In standard core-accretion models, most of the heavy elements are accreted during the core growth

• phase. (A small fraction is accreted during the

envelope collapse phase, when the increased gravitational reach brings a fresh supply of planetesimals). With pebble accretion, pebbles are efficiently accreted until the planet reaches the pebble isolation mass (~20 MEarth). The rest of the accretion then most of the heavy elements are accreted during the core growth phase. (A small fraction is accreted during the envelope collapse phase, when the increased gravitational reach brings a fresh supply of planetesimals). (see Lambrechts et al. 2014)

0.1 0.3 0.5 1 3 5 10 30 rXfilter=1 [AU]

• 4
• 2

2 4 Log(Dust size) [cm]

• 6
• 4
• 2

2

. 1 0.1 1.0 1.0 1.0 10.0

Guillot et al. (2014) Log (Mprotoplanet) [MEarth]

Pollack et al. (1996)

The low-Z content of accreted gas

In standard core-accretion models, most of the heavy elements are accreted during the core growth

• phase. (A small fraction is accreted during the

envelope collapse phase, when the increased gravitational reach brings a fresh supply of planetesimals). With pebble accretion, pebbles are efficiently accreted until the planet reaches the pebble isolation mass (~20 MEarth). The rest of the accretion then most of the heavy elements are accreted during the core growth phase. (A small fraction is accreted during the envelope collapse phase, when the increased gravitational reach brings a fresh supply of planetesimals). (see Lambrechts et al. 2014)

0.1 0.3 0.5 1 3 5 10 30 rXfilter=1 [AU]

• 4
• 2

2 4 Log(Dust size) [cm]

• 6
• 4
• 2

2

. 1 0.1 1.0 1.0 1.0 10.0

Guillot et al. (2014) Log (Mprotoplanet) [MEarth]

Once the planet is formed, the efficiency of planetesimal capture drops (e.g., Guillot & Gladman 2000, Matter et al. 2009)

Enrichment of the envelopes

• Core accretion: planetesimals are

delivered onto the central core.

• Core accretion: planetesimals cannot

reach the core intact. (Podolak et al. 1988; Pollack et al. 1996)

• Envelope capture: accretion efficiency

drops (Guillot & Gladman 2000): core erosion?

• Present: enriched atmospheres.

Core erosion

A 5-20 MEarth core is expected for Jupiter, Saturn, Uranus and Neptune from formation models (see e.g. Mizuno 1980, Ikoma et al. 2001) Is the energy required to erode a primodial core available?

Core erosion

A 5-20 MEarth core is expected for Jupiter, Saturn, Uranus and Neptune from formation models (see e.g. Mizuno 1980, Ikoma et al. 2001) Is the energy required to erode a primodial core available?

Energy required to mix the core upward:

Core erosion

A 5-20 MEarth core is expected for Jupiter, Saturn, Uranus and Neptune from formation models (see e.g. Mizuno 1980, Ikoma et al. 2001) Is the energy required to erode a primodial core available?

Energy required to mix the core upward: Maximal core mass flux given intrinsic luminosity L1(t): ϖ≈3/10

χ≈0.1: assumes that 10% of the energy in the first convective cell is used to mix chemical elements

Core erosion

A 5-20 MEarth core is expected for Jupiter, Saturn, Uranus and Neptune from formation models (see e.g. Mizuno 1980, Ikoma et al. 2001) Is the energy required to erode a primodial core available?

Jupiter Saturn

Energy required to mix the core upward: Maximal core mass flux given intrinsic luminosity L1(t): ϖ≈3/10

χ≈0.1: assumes that 10% of the energy in the first convective cell is used to mix chemical elements Guillot, Stevenson, Hubbard & Saumon (2004)

Core erosion

Are elements in the core miscible with metallic hydrogen?

Core erosion

Are elements in the core miscible with metallic hydrogen?

Wilson & Militzer (2011)

Water

Core erosion

Are elements in the core miscible with metallic hydrogen?

Wilson & Militzer (2011) Wilson & Militzer (2012)

Water Silicates

Core erosion

Are elements in the core miscible with metallic hydrogen?

Wilson & Militzer (2011) Wilson & Militzer (2012)

Water Silicates

Core erosion is possible because the elements involved are miscible in metallic hydrogen

The noble gases (+N2)

PH3-5.67H2O Xe-5.75H2O Kr Ar Thermodynamic path

• f the Solar nebula

between 5 and 20 AU

Delivered with ices as clathrates

The noble gases (+N2)

PH3-5.67H2O Xe-5.75H2O Kr Ar Thermodynamic path

• f the Solar nebula

between 5 and 20 AU

Delivered with ices as clathrates

Gautier et al. (2001), Alibert et al. (2005), Mousis et al. (2009) Guillot & Hueso (2006)

The noble gases (+N2)

PH3-5.67H2O Xe-5.75H2O Kr Ar Thermodynamic path

• f the Solar nebula

between 5 and 20 AU

Delivered with ices as clathrates

• r

Gautier et al. (2001), Alibert et al. (2005), Mousis et al. (2009) Guillot & Hueso (2006)

The noble gases (+N2)

PH3-5.67H2O Xe-5.75H2O Kr Ar Thermodynamic path

• f the Solar nebula

between 5 and 20 AU

T~10-30K

Low-temperature grains capture gases and settle to the disk mid-plane. Grains migrate in. Some volatiles may be released, but they do not reach the higher altitudes of the disk due to the negative temperature gradient there. The upper atmosphere of the disk evaporates due to radiation from the parent star (3a) and from external radiations (3b). This upper atmosphere contains moslty hydrogen and helium. Giant protoplanets gradually capture a disk gas which is enriched in non-hydrogen-helium species.

T~100K T ~ 1 , K T ~ 5 ~ 6 K

1 2 3a 4 3b 1 2 3 4 H-He photoevaporation H-He photoevaporation

Delivered with ices as clathrates Disk enriched by H-He photoevaporation

• r

Gautier et al. (2001), Alibert et al. (2005), Mousis et al. (2009) Guillot & Hueso (2006) see also Throop & Bally (2010)

Interior vs. Atmosphere

Giant exoplanets

Mass-Radius diagram

[Fe/H]

• 0.60

0.00 0.60

M* [MSun]

0.3 1.0 3.0

Transit Rad Vel Imaging

1 10 10

2

10

3

10

4

5 10 15 20 25 30

2013.09.30

1 10 10

2

10

3

10

4

Mass [MEarth] 5 10 15 20 25 30 Radius [REarth]

Examples of bulk composition determination

Examples of bulk composition determination

CoRoT

• 20b

Deleuil et al. (2012)

CoRoT

• 17b

Csizmadia et al. (2011)

CoRoT

• 27b

Parvainen et al. (2014) Models by M. Havel using CESAM

Heavily irradiated planets & “missing physics”

CoRoT

• 11b

Gandolfi et al. (2010)

Heavily irradiated planets & “missing physics”

CoRoT

• 11b

Gandolfi et al. (2010)

“Missing physics”

Heavily irradiated planets & “missing physics”

CoRoT

• 11b

Gandolfi et al. (2010)

“Missing physics”

magnitude frequency a dependence [Fe/H] dependence age dependence Refs interior/atmosphere

• pacities

√ √ ~ yes weak

Guillot et al. (2006), Burrows et al. (2007), Guillot(2008)

Semi-convection

√ ? X yes weak

Chabrier & Baraffe (2007)

K.E. model

√ √ √ no no

Guillot & Showman (2002), Burkert et al. (2005), Guillot et al. (2006, 2008)

Ohmic dissipation

√ √ √ yes no/yes

Laine et al. (2009), Batygin & Stevenson (2010)

Thermal tides

√ √ √ no no

Arras & Socrates (2010), [but see Gu & Ogilvie (2009), Goodman (astroph)]

Obliquity tides

? X √ no weak

Winn & Holman (2005), Levrard et al. (2006), Fabrycky et al. (2006)

Eccentricity tides

√ ? √ no strong

Bodenheimer et al. (2001), Gu et al. (2003), Jackson et al. (2008a,b), Ibgui & Burrows (2009), Miller et al. (2009)

Mass of heavy elements vs. stellar [Fe/H]

Mass of heavy elements vs. stellar [Fe/H]

Guillot et al. (2006), Burrows et al. (2007), Guillot (2008), Miller & Fortney (2012), Moutou et al. (2013)

The importance of the radiative zone

The importance of the radiative zone

Guillot & Showman (2002)

The importance of the radiative zone

Can upward mixing persist in the radiative zone ?

Guillot & Showman (2002)

The importance of the radiative zone

Can upward mixing persist in the radiative zone ?

Kzz~5x108 /Pbar cm2/s

Parmentier et al. (2013) Guillot & Showman (2002)

The importance of the radiative zone

Can upward mixing persist in the radiative zone ?

Kzz~5x108 /Pbar cm2/s tmix~ Hp δRp / Kzz ~10 Pbar Myr

Parmentier et al. (2013) Guillot & Showman (2002)

The importance of the radiative zone

Jupiter Saturn

Can upward mixing persist in the radiative zone ?

Kzz~5x108 /Pbar cm2/s tmix~ Hp δRp / Kzz ~10 Pbar Myr

Parmentier et al. (2013)

Mixing is prevented when radiative zone reaches the ~1kbar level

! ¡Rough ¡estimate ¡!

Guillot & Showman (2002)

Possible scenario

Possible scenario

Hot Jupiters

Possible scenario

Hot Jupiters Gentle accretion

Possible scenario

Hot Jupiters Gentle accretion Low atmospheric abundance No correlation atmosphere/ interior

Possible scenario

Hot Jupiters Gentle accretion Low atmospheric abundance No correlation atmosphere/ interior Giant impacts Moderate to high atmospheric abundance correlation atmosphere/ interior

Possible scenario

Hot Jupiters Gentle accretion Low atmospheric abundance No correlation atmosphere/ interior Giant impacts Moderate to high atmospheric abundance correlation atmosphere/ interior Warm Jupiters correlation atmosphere/ interior

Perspectives

Perspectives

• Test formation models by comparing atmospheric

abundances of known planets to bulk composition.

• CHEOPS, TESS
• PLATO
• Juno

Juno project overview

Spacecraft:

• Spinning, polar orbiter spacecraft launches in August

2011 – 5-year cruise to Jupiter, JOI in July 2016 – 1 year operations, EOM via de-orbit into Jupiter in 2017

• Elliptical 11-day orbit swings below radiation belts to

minimize radiation exposure

• 2nd mission in NASA’s New Frontiers Program First

solar-powered mission to Jupiter

• Payload of eight science instruments to conduct

gravity, magnetic and atmospheric investigations, plus a camera for E/PO Science Objective: Improve our understanding of giant planet formation and evolution by studying Jupiter’s

• rigin, interior structure, atmospheric composition

and dynamics, and magnetosphere Principal Investigator: Dr. Scott Bolton Southwest Research Institute

Deep atmosphere & Interior structure

zonal harmonic degree n

Guillot et al. (2004) Kaspi et al. (2010)

Radiometry

Radiometry ¡probes ¡deep ¡ into ¡meteorological ¡layer ¡ Determines ¡and ¡maps ¡the ¡ water ¡and ¡ammonia ¡ abundances